The present invention relates to the field of thin film magnetic heads that employ a magnetoresistive layer and which are used as reproduction heads for magnetic disk devices.
In response to the increasing recording density of hard disk drives, reproduction heads are being developed with a narrower reproduction track width and greater reproduction output than those of conventional thin film magnetic heads. One of these new reproduction heads is a MR head which utilizes the magnetoresistive effect, in which electric resistance changes in response to changes in an externally applied magnetic field. Types using materials with greater magnetoresistive effect are called GMR heads.
FIG. 4 is a sectional view of a part of a conventional thin film magnetic head. In FIG. 4, an insulating base layer 21 made such as of alumina, a lower shield magnetic layer 22 made of soft magnetic material such as nickel and iron, a first insulating layer 23 made of a non-magnetic material such as alumina, and a magnetoresistive layer 24 are formed on a substrate (not illustrated) made such as of alumina/titanium carbide. In the magnetoresistive layer 24, a magnetic response region 24a is for generating normal signals and an unwanted signal generating region 24b generates unwanted signals when the current flows through this region. A magnetic bias layer 25, made such as of hard magnetic film and antiferromagnetic film, for applying a magnetic bias to the magnetoresistive layer 24; lead 26; and a second insulating layer 27 for covering the lead 26, etc. are also formed.
The end face of the tip of the lead 26 is tapered, and a first taper close to the magnetoresistive layer 24 is formed at a large angle xcex8, and a second taper far from the magnetoresistive layer 24 is formed at a smaller angle xcfx86. For simplification, the upper shielding magnetic layer formed on the second insulating layer 27 is not illustrated.
In the prior art shown in FIG. 4, the magnetic bias layer 25 is disposed in a clearance created on the first insulating layer 23, and the magnetoresistive layer 24 is formed on the magnetic bias layer 25 and the clearance. The tip of the lead 26 contacts the magnetoresistive layer 24 beyond the end of the magnetic bias layer 25.
In general, the magnetic response region 24a is approximately equivalent to the area between the tips of the leads 26. Strictly speaking, however, it is not electrically equivalent to the area between the tips of the leads 26 because the current from the lead 26 flows not only from the tip of the lead 26 but also extensively in the lengthwise direction of the lead 26.
In order to satisfy the increasing demand for higher recording density, the magnetic head needs to achieve a narrower reproduction track width by narrowing the magnetic response region but without degrading the sensitivity and S/N ratio. Accordingly, the current needs to be fed efficiently only to the magnetic response region, which is equivalent to the width of a track, without any current leakage to other regions.
In the aforementioned prior art, the width of the magnetic response region is accurately specified by forming the large angle xcex8 at the tip of the lead 26 against the main face of the magnetoresistive layer 24. The coverage of the second insulating layer 27 at the step portion is improved by forming a portion following the tip of the lead with a smaller angle xcfx86 for a gentle slope.
However, the magnetoresistive layer 24 is formed crossing the step portion at the tip of the magnetic bias layer 25, and this causes a different concern. More specifically, the magnetic bias layer 25 needs to be disposed as close as possible to the magnetic response layer 24a in order to efficiently apply a magnetic bias to the magnetic response layer 24a in the above conventional configuration. On the other hand, the tip of the magnetic bias layer 25 and the tip of the lead 26 also come closer when the magnetic bias layer 25 and the magnetic response layer 24a are in closer proximity. This requires that the lead 26 be thickened at the portion close to the magnetic bias layer 25, resulting in an overall increase in the thickness of the lead 26. Greater thickness at the tip of the lead 26, which is thickness of a slope portion having the angle xcex8, causes problems in coverage of the second insulating layer 27 at the step portion covering the lead 26, and occurrence of cracks.
Also in the conventional configuration, the lead 26 directly contacts the magnetoresistive layer 24, and this requires that a material for the lead 26 be selected for good adhesivity to the magnetoresistive layer 24 without causing a reaction with the magnetoresistive layer 24, resulting in many restrictions on its practical use.
The present invention aims to provide a thin film magnetic head which allows the accurate definition of the magnetic response region, to reduce current to the magnetoresistive layer at regions other than the magnetic response region, and to increase the S/N ratio by increasing the proportion of current flowing in the magnetic response region; and to offer a structure that is easy to manufacture.
The thin film magnetic head of the present invention includes an insulating base layer; a lower shield magnetic layer formed on the insulating base layer; a first insulating layer formed on the lower shield magnetic layer; a magnetoresistive layer formed selectively over at least a portion of the first insulating layer; a magnetic bias layer formed sandwiching the magnetoresistive layer for applying magnetic bias to the magnetoresistive layer; a pair of leads formed over at least a portion of the magnetic bias layer for detecting a change in electric resistance of the magnetoresistive layer by an external magnetic field; a non-magnetic cap layer formed under the lead between the lead and the magnetoresistive layer; a second insulating layer at least covering the magnetoresistive layer, magnetic bias layer, and pair of leads; and an upper shield magnetic layer formed on the second insulating layer.
In the above configuration, the non-magnetic cap layer under the leads accurate specification of the width of the magnetic response region, allowing the current to effectively flow from the lead to the magnetic response region.
Moreover, the thin film magnetic head of the present invention includes an insulating base layer; a lower shield magnetic layer formed on the insulating base layer; a first insulating layer formed on the lower shield magnetic layer; a magnetoresistive layer formed over at least a portion of the first insulating layer; a magnetic bias layer formed sandwiching the magnetoresistive layer for applying magnetic bias to the magnetoresistive layer; a non-magnetic cap layer formed on a main face of the magnetoresistive layer; a pair of leads formed over at least a portion of the magnetic layer for detecting a change in electric resistance of the magnetoresistive layer by an external magnetic field; a second insulating layer at least covering the magnetoresistive layer, magnetic bias layer; and pair of leads; and an upper shield magnetic layer formed on the second insulating layer. The portion of the non-magnetic cap layer under the lead is thicker than the portion of the non-magnetic cap layer not under the lead.
This configuration enables to effectively protect the main face of the magnetoresistive layer in the manufacturing process, and, at the same time, the thick non-magnetic cap layer under the leads enables to accurately specify the width of the magnetic response region, allowing the current to effectively flow is from the lead to the magnetic response region.
Still more, the thin film magnetic head of the present invention includes an insulating base layer; a lower shield magnetic layer formed on the insulating base layer; a first insulating layer formed on the lower shield magnetic layer; a magnetoresistive layer formed over at least a portion of the first insulating layer; a magnetic bias layer formed sandwiching the magnetoresistive layer for applying magnetic bias to the magnetoresistive layer; a first non-magnetic cap layer formed on a main face of the magnetoresistive layer; a pair of leads formed over at least a portion of the magnetic bias layer for detecting a change in electric resistance of the magnetoresistive layer by an external magnetic field; a second non-magnetic cap layer under the lead between the lead and the first non-magnetic cap layer; a second insulating layer at least covering the magnetoresistive layer, magnetic bias layer, and pair of leads; and an upper shield magnetic layer formed on the second insulating layer.
The above configuration enables to demonstrate stronger effect by selecting appropriate materials for the first and second non-magnetic cap layers. In addition, a material for the first non-magnetic cap layer is selectable with respect to increased adhesivity to the second non-magnetic cap layer and preventing reaction between the magnetoresistive layer and second non-magnetic cap layer.
Still more, the above thin film magnetic head of the present invention has the configuration that the top face of the non-magnetic cap layer under the lead and the main face of the magnetic bias layer are approximately leveled. This reduces a step at the top end of the magnetic bias layer, enabling to make the lead thinner, and solve problems of the coverage by the second insulating layer and occurrence of cracks, and so on.
Still more, the above thin film magnetic head of the present invention has the configuration that opposing end faces of the non-magnetic cap layers under the lead form an angle xcex81 against the main face of the magnetoresistive layer, and the top end face of the pair of leads form an angle xcfx861 against the main face of the non-magnetic cap layer. In addition, xcex81 and xcfx861 satisfy the relation of xcfx861 less than xcex81 less than 90xc2x0. This enables to easily and accurately specify the magnetic response region using the top ends of the non-magnetic cap layers.
Still more, the above thin film magnetic head of the present invention has the configuration that the sheet resistance of a thin portion of the non-magnetic cap layer sandwiched with the tips of the leads on the main face of the magnetoresistive layer is higher than the sheet resistance of the magnetoresistive layer. This enables to supply a larger proportion of current to the magnetoresistive layer than that to the thin non-magnetic cap layer, allowing to increase the S/N ratio.
Still more, the above thin film magnetic head of the present invention has the configuration that the specific resistivity xcfx811 of the first non-magnetic cap layer and the specific resistivity xcfx812 of the second non-magnetic cap layer satisfy xcfx811 greater than xcfx812. This enables to prevent the current supplied to the second non-magnetic cap layer from reaching the first non-magnetic cap layer adjacent to the magnetoresistive region, allowing increased current directed to the magnetoresistive region for increasing the S/N ratio.
Still more, the above thin film magnetic head of the present invention has the configuration that the specific resistivity xcfx811 of the first non-magnetic cap layer, the specific resistivity xcfx812 of the second non-magnetic cap layer, and the specific resistivity xcfx813 of the third non-magnetic cap layer satisfy xcfx811 greater than xcfx813 greater than xcfx812. By specifying the relation of specific resistivity in each layer, the current is effectively fed from the lead to the magnetoresistive region, allowing to increase the S/N ratio.
Still more, the above thin film magnetic head of the present invention has the configuration that a thickness t1 of the non-magnetic cap layer under the lead, a thickness t2 of the non-magnetic cap layer on the magnetoresistive layer at portions other than that under the lead satisfy t2 less than (t1-t2). This enables to limit the current flowing through the non-magnetic cap layer on the magnetoresistive layer and enhances the current flow at a portion of the non-magnetic cap layer under the lead, resulting in increasing the S/N ratio.
Still more, the above thin film magnetic head of the present invention has the configuration that a thickness t3 of the first non-magnetic cap layer and a thickness t4 of the second non-magnetic cap layer satisfy t3 less than t4. This enables to relatively increase the current flowing to the magnetoresistive region, resulting in increasing the S/N ratio.
Still more, the above thin film magnetic head of the present invention has the configuration that the sheet resistance of the non-magnetic cap layer formed under the pair of leads is lower than the sheet resistance of the magnetoresistive layer. This enhances the current from the magnetic bias layer to be fed to the magnetic response region through the tip of the non-magnetic cap layer, reducing the current flowing to the unwanted signal generating region, and thus increasing the S/N ratio.
As described above, the thin film magnetic head of the present invention selectively provides the magnetic bias layer on both sides of the magnetoresistive layer, and the pair of leads are connected to the magnetoresistive layer through the non-magnetic cap layer provided under the lead. This enables to accurately specify the magnetoresistive region using the tip of the non-magnetic cap layer, and also enables to effectively feed the current from the lead to the magnetoresistive region by effectively concentrating the current on the tip of the non-magnetic cap layer.
Still more, a first non-magnetic cap layer formed over an entire main face of the magnetoresistive layer and a second non-magnetic cap layer provided under the lead between the lead and the first non-magnetic cap layer enable to broaden a choice of material for the non-magnetic cap layer, realizing a thin film magnetic head with high accuracy and high reliability.
Still more, if a main face of the non-magnetic cap layer under the lead and a main face of the magnetic bias layer are approximately leveled, the lead may be formed almost without any step. This allows to thin the lead, making the step seen from the second insulating layer smaller compared to the prior art.
In addition, the angle between the end face of the non-magnetic cap layer and the main face of the magnetoresistive layer may be made large. This makes the current efficiently flow only to the magnetic response region, improving the S/N ratio. At the same time, a gentle slope at the lead tip prevents an insufficient coverage or cracks of the insulating film covering the lead at the step portion.
In each of the above configurations, a relation among a sheet resistance between the non-magnetic cap layer and magnetoresistive layer, specific resistivity, and film thickness may be appropriately set to increase the current fed to the magnetic response region for improving the S/N ratio.
The non-magnetic cap layer described in the present invention is formed on an uppermost layer of the magnetoresistive layer. An expression of the magnetoresistive layer may include the non-magnetic cap layer in some descriptions. However, for easier understanding in the present invention, the magnetoresistive layer refers to an overlayed film having a magnetoresistive effect, and a non-magnetic cap layer refers to a layer formed on the magnetoresistive layer. Accordingly, the non-magnetic cap layer also refers to the layer formed over a part of the overlayed film having magnetoresistive effect, a non-magnetic cap layer configured with multiple layers. Furthermore, the term non-magnetic cap layer is used regardless of a purpose or effect on an overlayed film having a magnetoresistive effect.